Bookcase



FIG. 1 is a perspective view of a bookcase showing my new design;

FIG. 2 is a front elevation view thereof; and,

FIG. 3 is a left side elevation view thereof.

The broken lines showing is included for the purpose of illustrating environment of the design and forms no part of the claimed design.

The broken lines that define the bounds of the claimed design form no part thereof. 

The ornamental design for a bookcase, as shown and described. 